And the winner is...
Hart Foundation gives award for exceptional automation solution

At the end of last year, the US-based Hart Communication Foundation gave its “Plant of the Year” award for the first time to a European system. This article briefly describes the automation project and explains what is so special about it.


Additives are required in most of today’s plastics applications to reduce breakup of the long polymer chains and increase the useful life of products that are exposed to sunlight. Clariant produces light stabilizers and anti-oxidants at its Gersthofen plant. The production systems, which are also used to test new products, have been continually updated in recent years to reflect the current state of technology, and process flows were included in this retrofit activity. As a result, the automation systems are not standardized. For example, pneumatic equipment runs in parallel with electrical instrumentation. The lack of a central control room has also posed a problem. The electrical devices were distributed over a number of different machine rooms. To meet Ex-Zone 1 IIc requirements, the Facilities Engineering Department decided to install an intrinsically safe remote I/O system supplied by Stahl. The devices use an intrinsically safe Profibus to transmit a standard 4-20 mA signal from Hart-enabled transducers to the Profibus master, in this case an Emerson DeltaV process control system.

This configuration has a number of advantages. The intrinsically-safe Profibus, which is installed in the Ex zone and runs at 1.5M Baud, can be used for very high speed data transfer. On-site installation minimizes the length of the cables which are routed to the field devices, and this quickly becomes very obvious. Less time and material are required for installation, and the electrical documentation is less complex because fewer terminals are needed. The user also has all the benefits of intrinsically safe field device connections. For example, all of the devices can be attached to or removed from the I/O system without the need to take any special precautions. This is particularly helpful during initial installation.
Programming on site
In the past, a PC with the appropriate Ex safety rating was needed to set parameters in field devices which were already installed. This type of programming, either under central control or on site, is indispensable with today’s transducers, because they often have to be modified to work under different process conditions or with a different product. It can be difficult to access some field devices with a notebook. In addition, a variety of proprietary software and interfaces are needed to handle devices supplied by a number of different manufacturers (e.g. ABB, E+H, Vega). A standardized approach to diagnostics was virtually impossible. Facilities Engineering wanted to parameterize the devices while they were installed, ideally from a central workstation in the control rooms or in an office using software which is compatible with all device types and suppliers.
To meet these requirements, the Profibus had to be linked into the factory network. The engineers used a Fieldgate FG300 which was supplied by Softing. The
Ethernet/ Profibus Gateway allows an authorized office computer to access the Profibus. Access modules also had to be used on the Stahl remote I/O units which support both cyclic DP services and acyclic DP/V1 services for Hart-on-DP communications.
The Facilities Engineering Department decided to use Pactware as the frame application on this project. The basic version of the software is available on the Internet, and the full version is reasonably priced. There are no additional ongoing costs. The freedom to expand the system without having to pay additional license fees is another advantage. The FDT solution differs in this respect from asset management solutions offered by process control system suppliers. The proprietary device drivers (DTM) are linked into the FDT frame application. Users have access to the full parameter set in all of the devices. The ability to display envelopes from radar level sensors was another argument in favor of this solution. Even if there is no DTM available for a device, a generic DTM can be used to modify or display certain parameters. In Pactware, the device DTMs describe the complete topology of the control system. The first step is to set the Ethernet address and transmission data in the device DTM. Then the Profibus address of the field station is set in the communications DTM, which is used by the remote I/O devices. All of the field devices that are connected to this station are created at this address using a channel list. So it is possible to use the specific driver to access any device which is attached.
Link to the Profibus
The latest generation of Stahl remote I/O units offers a potentially useful way to use Hart communications technology. The extended parameter set can directly send available process variables, for example a status signal from a Hart actuator or the temperature of a pressure transducer, as floating point variables on the Profibus. These variables can be used as standard signals on the process control system. The Hart variables are set in the remote I/O configuration, for example the second Hart variable can be handled by the first input and the fourth variable can be handled by the third input. Using this method, an eight line Stahl input or output module can handle eight additional signals. This eliminates the need to install feedback contacts for an actuator, because the same 4...20 mA control lines can be used. The beauty of this solution is that it works with all Profibus-enabled control systems and there is no dependency on the control system manufacturer, because in this case the intelligence is located in the peripherals.
High-speed access
The advantages of this approach are obvious. Access to all of the installed devices is faster and more cost effective. Parameters can easily be set from an office PC, and preventive maintenance can be run by the plant facilities maintenance team. When a device has a fault, the stored configuration can quickly be transferred from the defective unit to the replacement device. This eliminates the need to keep a stock of spare parameterized devices, and users have the flexibility to use non-parameterized generic devices in a number of different locations. There is no need to wait for permits to be issued. Troubleshooting and repair can begin as soon as the operators report a fault, and FDT is a very useful tool for this activity as well. Diagnostic tools are available which greatly simplify troubleshooting. An added advantage is the fact that parameterization of all field devices takes place using the same software environment, which handles configuration management and documentation.
Now that this Facilities Engineering project has been completed at Clariant, only minor effort is needed to fully utilize Hart devices which have been installed for years. Only minor problems had to be corrected during the start up phase (e.g. lost tokens and compatibility problems between devices), and close cooperation between employees from Stahl and Softing ensured that problems were resolved quickly. Tests were then conducted on the system, and this allowed device manufacturers to make improvements to their software. When all of the work was completed, Clariant was able to put a fully functional, highly-automated system into operation. The low incremental investment costs were amortized within a short period of time due to increased system availability and reduced idle time. The results were enough to convince the Hart Plant of the Year jury.